Radio-frequency inductance coils



Y 195.2 R. A. WILSON 2,598,089

RADIO-FREQUENCY INDUCTANCE COILS Filed March 16, 1949 Rwy/2m Auar M1 5011/ Patented May 27, 1952 UNITED STATES ATENT OFFICE Application March 16, 1949, Serial No. 81,667 In Great Britain March 18, 1948 Claims. 1

The present invention relates to inductance coils for use at radio frequencies, for example in radio receivers.

It is the object of the present invention to provide a radio frequency inductance coil which, while efficient in operation, is nevertheless compact and cheap to produce.

According to the present invention, a radio frequency inductance coil comprises a hollow former of insulating material, a coil wound upon the former, one plate of a trimming condenser, which condenser is electrically connected to the coil to serve as a trimmer therefor, arranged to be supported upon one end of the former, a second plate of the condenser separated from the first named plate by an insulating member and means for adjusting the average spacing between the said plates to vary the capacity of the trimming condenser.

Tags of U shape are preferably provided having at least one of their two limbs projecting through apertures in the former, the tags being held in position by a closure member of insulating material inserted into one end of the former. This closure member may form a seating for the firstnamed plate of the condenser.

An iron dust core is preferably adjustably mounted within the hollow former. This core may be adjusted along a threaded screw arranged coaxial with the former. This threaded member may extend at one end from the former and constitute anchoring means whereby the coil can be attached to a support. The same threaded member may extend through the closed end of the former and a nut'or the like threaded there on may provide the required adjustment of the trimming condenser. One of the two plates of the condenser may be bowed in such a manner that by rotation of the said nut the average spacing between the two plates is varied.

One embodiment of the present invention will be described by way of example with reference to the accompanying drawing, in which Figure 1 is an exploded front view of the embodiment, Figure 2 shows at (a) and (b) in plan and front elevation respectively one condenser plate in the embodiment of Figure 1, Figure 3 is a view in elevation of one of the U-shaped contact tags in Figure l, and Figure 4 is a view in front elevation of the arrangement of Figure 1 assembled.

Referring to the drawing, a coil former consists of a tube IU of suitable insulating material and a closure member II which may be of the same material. This material may for example be polystyrene, The portion I2 of the member II is of reduced diameter adapted to fit within the tube I0. When the member II is forced into position in one end of the tube IE, it serves to lock therein four symmetrically-disposed appr ximately U-shaped tags I 3. These tags serve as terminals for coils I4 and I4 which may be of any known or suitable type wound about the former It. The tags I3 are located by means of shall-ow recesses I5 in one end of the tube II and one arm of each tag projects through a rectangular aperture I6 in the former Ill.

The member II may be fixed within the tube It by the use of a suitable solvent or other adhesive. In a threaded aperture in the member I I is a threaded rod I'I locked in position within the member II by means of a nut I8. The rod IT carries a dust-iron core I9 which can be rotated around the threaded rod and so adjusted in longitudinal position within the former Ill.

Upon the surface 20 of the member II is disposed a fiat metal Washer 2I having a central clearance aperture for the rod I'I. This washer has a downwardly turned lug 22 and two small downwardly turned lugs '23, the three lugs serving to locate the washer in its correct position relatively to the member II, that is to say out of contact with the rod I'I. Upon the washer 2| is arranged an insulating member 24 also having a clearance aperture for the threaded rod 11. The washer 24 may, for example, be of mica. Above the washer 24 is arranged a member 25, shown most clearly in the plan and front elevation views of Figure 2 (a) and (b) respectively, which may be formed from a flat, circular washer bent into bowed form with its concave side downward and having its edges bent upwards as at 25, in order to present rounded surfaces 21 to the washer 24. The washers 2| and 25 are preferably of German silver. Above the bowed wash-er 25 is a plain washer 28 and a nut 29 is threaded on to the upper end of the rod Il. As the nut '29 is screwed further on to the rod I? the condenser, consisting of the plates 2| and 2&3 with the insulating member 24 between them, has its capacity progressively increased owing to the flattening of the bowed washer 25. The bowed washer 25 also acts to lock the nut 29 and prevent its becoming unscrewed.

The lug 22 on the washer 2| is fixed for example by spot welding to one of the tags I3.

When the coil has been assembled the iron core i9 is adjusted along the rod II to such a position that the coil has the desired performance and the core It is then locked in position, for instance, by inserting a small amount of adhesive either between the core 19 and the rod H, or between the core l9 and the interior wall of the tube Iii. The portion of the rod I! which projects beneath the tube It) may be employed for mounting the coil assembly upon a chassis or other support, and for this purpose a nut 3G is provided.

The wiring between the coils l4 and I4 and the tags [3 is shown diagrammatically. In the case of coils for medium frequencies the wiring may conveniently pass within the hollow former. For higher frequency coils external, short lengths of wire are preferably used.

It will be seen that the coil above describedis simple to construct and it is also compact since the space occupied by the trimming condenser is extremely small relatively to the space occupied by the remainder of the assembly.

I claim:

1. A combined radio frequency inductance coil and trimmer for mounting as a unit upon a panel, comprising a hollow cylindrical former of insulating material, a closure member of insulating material closing one end of said former, a coil wound upon the outer surface of said former, a first plate of a trimming condenser for said coil supported upon the outer surface of said closure member, a second plate for said condenser, an insulating layer between said first and second plates and threaded means substantially coaxial with said former means for adjusting the average spacing between said plates to vary the capacity of the trimming condenser.

2. A radio fr quency inductance coil comprising a hollow cylindrical former of insulating material, a closure member of insulating material closing one end of said former, said closure member having a plug portion within said former, at least one U-shaped contact member having one limb projecting outwardly through an aperture in said former, said plug portion engaging and clamping said contact) member, a coil wound upon said former, and a variable trimming condenser for said coil supported upon the outer surface of said closure member.

3. A combined radio frequency inductance coil and trimmer for mounting as a unit upon a panel, comprising a hollow cylindrical former of insulating material, a closure member of of said closure member and having a clearance aperture for said rod, a second plate for said condenser apertured for the passage of said rod therethrough, an insulating layer between said plates, one of said plates being bowed, an electrical connection between said first plate and said coil and a nut threaded upon said rod to vary the bowing of said one of said plates and thereby vary the capacitance of said condenser.

4. A combined inductance coil and trimmer according to claim 3, comprising a core of powdered magnetic material threaded upon said rod.

5; A combined radio frequency inductance coiland-trimmer for mounting as a unit upon a panel, comprising a hollow cylindrical former of insulating material, a closure member of insulating material closing one end of said former, a coil wound upon the outer surface of saidformen-a threaded metal rod fixed to said-closure member, a first plate of a trimming condenser for said coil supported upon the outer surface of said closure member, having a clearance-aperture for said rod and having at least three lugs projecting therefrom and engaging the outer surface of said closure member to locate said first plate out of contact with said rod, a second plate for said condenser apertured for the passage of said rod therethrough, an' insulating layer between said plates,-one of said plates being bowed, an electrical connection between said first plate and said coiland a nut threaded upon said rod to vary the bowing of said one of said plates and thereby vary the capacitance of said condenser;

RONALD ALBERT IL-SON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,014,820 Snider Sept. 17, 1935 2,168,351 La Rue et al Aug. 8, 1939 2,196,147 Dunn Apr. 2, 1940 FOREIGN PATENTS Number Country Date 272,721 Great Britain June 23, 1927 16,772/34 Australia Feb. 6, 1935 OTHER REFERENCES Se'r. No. 342,615, 1 Bergtold (A. P. 0.), nublished May 25, 1943. 

